Flow regime transitions in gas-liquid co-current upward transport are analyzed by analogy to gas-solids upward transport. The transition from bubbly flow to slug flow of gas-liquid transport is well predicted by extending an analysis used for gas-solids systems. The transition from slug to churn flow in gas-liquid systems is analogous to the transition from slugging to turbulent fluidization. The transition velocity in gas-liquid systems based on visual observation is found to be close to the point where the maximum of the standard deviation of absolute pressure fluctuations reaches a maximum, the criterion commonly employed to define the onset of turbulent fluidization. The transition from churn to annular flow is also analogous to the transition from fast fluidization to dilute pneumatic transport in gas-solids systems. The data on transition from churn to annular flow is analyzed systematically and compared with available correlations.